Just so we're on the same page (ahah).
THIS :
... is a 2 pages spread right ?
It's the most horizontal you can get. So for those of us who want to keep their comic in an horizontal format (like a classic book or something) to make a printed version or whatever, it's a bit hard to make a 2-pages spread, so it would be great if we could get a bigger image just by clicking on it...
As for the screen, even if we have 16/9 screens, when you're on internet, nothing is horizontal anymore, you're supposed to scroll vertically...
For the vertical comics, the rythm is so completely different and the panels spread so differently that we can't talk about pages anymore. They're "webcomics" not meant to be printed, so no pages.
So to me, a 2-pages spread definitely belongs to the horizontal comics.